Method for preparing styrene/isoprene in-situ toughened polypropylene

Abstract

The invention discloses a method for preparing styrene / isoprene in-situ toughened polypropylene, and relates to a method for preparing styrene / isoprene in-situ toughened polypropylene by reactive extrusion. According to the method, raw materials comprise polypropylene, styrene, isoprene and a peroxide initiator. The method is characterized by comprising the following steps of: adding the polypropylene from a main charging hole of a first section of an extruder; injecting styrene, isoprene monomers and the peroxide initiator into a third section of the extruder by a metering pump; and performing melt grafting at the reaction temperature of between 170 and 230 DEG C to obtain the in-situ toughened polypropylene material with high melt strength, wherein the toughness of the polypropylene can be improved obviously under the condition of the low using quantity of the monomers, the breakage elongation can be increased to 65 percent, and tensile strength of the polypropylene is equal to and even higher than that of pure polypropylene; and by the method, a toughening effect of a blending system of the polypropylene and 5 percent of butadiene-styrene-butadiene (SBS) can be achieved. According to the method, a process is simple, easy to control, low in cost and environment-friendly, and the product can be used for foaming and can be used as engineering stressed materials to be applied to the field of automobile industry.

Description

Technical field [0001] The invention relates to a method for preparing in-situ toughened polypropylene, in particular to a method for preparing styrene and isoprene co-grafted polypropylene by reactive extrusion. Background technique [0002] Polypropylene (PP) has become increasingly important in the plastic family for its excellent heat resistance and environmental friendliness. However, the semi-crystalline structure of PP leads to its low-temperature brittleness and poor impact performance, which limits its application in the field of engineering stressed materials. Therefore, the toughening modification of polypropylene in order to improve its toughness becomes the key technology. [0003] At present, the methods of toughening and modifying polypropylene are blending toughening, shape control toughening, cross-linking toughening, low foaming toughening, etc. Among them, blending modification is the most common, which uses similar solubility parameters. Reaction principle: Two...

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Problems solved by technology

[0004] Chinese patent CN102504406A uses bis-tert-butyl peroxide as vulcanizing agent, sulfur as co-vulcanizing agent, and ethylene-vinyl acetate copolymer as toughening agent to modify polypropylene. The impact strength of the product obtained in this invention is higher than that of pure polypropylene It has increased by about one time, and the melt index has also dropped significantly. The toughening agent is uniformly dispersed in the polypropylene matrix with a smaller particle size, but due to the use of sulfur, the smell is very heavy

However, the patented process is complicated, and the nanoparticles increase the cost

[0006] Chinese patent CN101698722A provides a method for preparing ethylene-propylene rubber grafted maleic anhydride modified polypropylene toughening masterbatch, the impact strength of the product can be increased by 20 times, but the addition of ethylene-propylene rubber is 15 to 25 parts, which is bound to Tensile strength and modulus of sacrificial polypropylene matrix

[0007] Chinese patent CN102432762A provides a method for preparing grafted polypropylene with high melt strength, using maleic anhydride, isoprene, and styrene as modified monomers, and the melt index of the obtained product can be reduced by up to 85%. The sag value at 190°C is 12-19.5cm, and the melt strength is greatly improved, but the invention does not involve the mechanical properties of the product

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